Apparatus for continuously depositing beryllia through vaporization of a basic formate

ABSTRACT

An apparatus for vaporizing a basic formate of beryllium by continuous means in which the beryllium basic formate is mixed with a granular inert carrier material such as sand and as an aggregate is fed from a storage hopper through a closed screw conveyor system through a heating zone whereat the basic formate of beryllium is vaporized and in a vaporized condition is delivered to a chamber in which the beryllium basic formate is thermally decomposed into beryllia and is deposited on a substrate. The granular inert material and unvaporized basic format is discharged to a closed receiving hopper for reprocessing and the like.

Unite States Patent [1 1 [111 3,754,529

Fleischner [4 Aug. 28, 1973 [54] APPARATUS FOR CONTINUOUSLY 3,414,42812/1968 Kelly et al. 117/ 107.2 P

nerosn'mc BERYLLIA rnaoucn 3,449.1

VAPORIZATION OF A BASIC FORMATE 6/1969 Baldi 118/48 X PrimaryExaminer-Morris Kaplan Attorney-Ralph R. Roberts [5 7] ABSTRACT Anapparatus for vaporizing a basic formate of beryllium by continuousmeans in which the beryllium basic formate is mixed with a granularinert carrier material such as sand and as an aggregate is fed from astorage hopper through a closed screw conveyor system through a heatingzone whereat the basic formate of beryllium is vaporized and in avaporized condition is delivered to a chamber in which the berylliumbasic formate is thermally decomposed into beryllia and is deposited ona substrate. The granular inert material and unvaporized basic formateis discharged to a closed receiving hopper for reprocessing and thelike.

7 Claims, 3 Drawing Figures APPARATUS FOR CONTINUOUSLY DEPOSITINGBERYLLIA THROUGH VAPORIZATION OF A BASIC FORMATE DIVISIONAI. APPLICATIONThis is a Divisional Application of Application Ser. No. 44,344 filedJune 8th, 1970, now U.S. Pat. No. 3,679,463, in the name of the presentApplicant.

DESCRIPTION OF THE PRIOR ART The particular physical qualities of BeOhas made the dense coating of substrates with BeO highly desirable andcommercially used. One method or process for producing such a densecoating of BeO is disclosed in U.S. Pat. No. 3,484,278 which issued Dec.16th, 1969, with TABEL and HOEKSTRA as inventors. As seen in FIG. 1 ofthis patent, the reduction to practice and teaching discloses knownlaboratory equipment such as a bell jar. The resulting coating ofsubstrates is satisfactory as to its composition, structure and use, butfrom an economical standpoint the labor cost per piece exceeds thedesired practical level. It is also to be noted that all exposedsurfaces within the bell jar 10 are given substantially the same amountof deposition of BeO. On the substrates to be plated this is desirous;on the equipment including the inside of the bell jar this is not only awaste, but often requires removal before the equipment can again beused. The information and description provided in U.S. Pat. No.3,484,278 aboveidentified is incorporated by reference into thisapplication.

Conveying systems are of course well known and certain processingsystems are representatively shown in U.S. Pat. No. 3,176,970 toHOLCROFT of Apr. 6th, 1965 and in U.S. Pat. No. 3,497,914 to TYBOUT ofMar. 3rd, 1970. In these and other systems, insofar as is known, thereis no showing of a closed conveyor system wherein in one portion thereis provided a heating region whereat the metal is vaporizedand collectedand then is conducted or transported to a deposition chamber wherein thewall is made porous so as to enable passage therethrough of pressurizeddry air and the like. This pressurized gas is forced inwardly throughthe wall so that the vaporized beryllium basic formate is prevented fromcoming in contact with the wall or walls of the deposition chamber.

Deposition chambers for gas or vapor plating are representatively shownin U.S. Pat. No. 2,905,573 to MARVIN issuing Sept. 22nd, 1959; U.S. Pat.No. 2,921,868 to BERGER issuing Jan. 19th, 1960, and in U.S. Pat. No.2,929,739 to BREINING et al., issuing Mar. 22nd, 1960. These and otherpatents show tubular inner chambers but, insofar as is known, the use ofpressurized dry air or gas through a porous inner wall of a chamber tomaintain the inner wall surface in an uncoated condition is novel andprovides a means for commercial coating of substrates with denseberyllia.

SUMMARY OF THE INVENTION The present invention may be summarized atleast in part with reference to its objects. It is an object of thisinvention to provide an apparatus for continuously producing a berylliumbasic formate vapor by heating an aggregate containing a portion ofbasic formate of be ryllium as the aggregate is transported by a screwconveyor through a heating zone. This formate vapor is collected in ahood chamber and from this chamber is fed through a conductor or pipe toa chamber in which the substrates to be coated are placed.

It is a further object of this invention to provide an apparatus forproducing and depositing beryllia on substrates in which a basic formateof beryllium is mixed with an inert granular material such as sand andby and in a closed conveyor system is brought to and through a heatingzone whereat the basic formate of beryllium is vaporized and in agaseous condition is fed to a deposition chamber in which substrates areplaced for thermally decomposing beryllium basic formate to provide harddense beryllia deposits on a substrate heated to a temperature of250-600 C. The inner walls of the deposition chamber are of a porousconstruction to the extent that dry air, gas and the like may be forcedthrough the porous wall to provide a gas liner or curtain inhibiting thedeposition of the beryllia on the inner surface pf the chamber walls.

In the apparatus to be more fully described hereinafter, a berylliumbasic formate is mixed with a granular inert material such as sand. Themixture is preferably about 5 to 10 percent basic formate by weight withthe balance an inert carrier material such as sand. From a hopper, thismixture is discharged to a screw conveyor which is sealed except for theinlet from the hopper and an outlet into a sealed vertical dischargechute to the inlet end of yetanother sealed screw conveyor. Towards thedischarge end of this conveyor, the trough walls are made porous and areenclosed in a heat zone of chamber provided to locally heat this area to150 to 300 centigrade. This temperature is sufficient to vaporize thebasic formate of beryllium at an to percent efficiency. The vapor passesthrough the porous passageways while residue granular ash and sand aredischarged at the end of the conveyor into a sealed chute and intoanother sealed conveyor to discharge into another sealed chute andsealed hopper where it is accumulated for disposal or reprocessing.

The vaprozied basic formate of beryllium is collected in an aspiratingchamber above the conveyor and from this chamber is fed by a tubularconductor to a deposition chamber having an inner wall of a porousconstruction. The vapor is fed to and into this inner chamber so as tobe brought in way of the substrate to be coated. The outer portion ofthe deposition chamber is fed with pressurized dry air or the like whichis permitted to flow in a determined amount through the porous wall soas to push the vaporized basic formate of beryllium delivered into theinner chamber from any plating contact with the wall of the innerchamber.

INTENT OF THE DISCLOSURE V There has been chosen a specific embodimentof the apparatus for continuously vaporizing a basic formate ofberyllium and through a conductor feeding this vapor to a preferreddeposition chamber for plating substrates with dense BeO. This specificembodiment has been chosen for the purposes of illustration anddescription as shown in the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 represents a somewhat schematicside view of a preferred conveying and vaporizing apparatus of thisinvention;

FIG. 2 represents an enlarged sectional side view of a depositionchamber adapted for transmitting a vaporspecification discloses certaindetails of construction for the purpose of explanation of the broaderaspects of the invention, but it should be understood that structuraldetails may be modified in various respects without departures from theconcept and principles of the invention and that the invention may beincorporated in other structural forms than shown.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the schematicside view of FIG. 1 it is to be noted that a conveying and vaporizingapparatus includes a base 10 upon which a support 11 carries a hopper 12within which is stored an aggregate 13 consisting of a basic formate ofberyllium and a granular inert carrier material such as sand. Thishopper is provided with a discharge chute 14 disposed to control theflow of aggregate material from hopper 12 to a screw conveyor 16 divenby a motor 18 through coupling shaft 20. The housing 21 for the conveyor16 is sealed with the rear end of the conveyor housing 21 having aclosed end member 22 to prevent any gas back up or dust from theconveyor 16 to and out the rear end of the conveyor as berylliumcompounds and their va-' pors are highly toxic. A bearing 24 supportsthe conveyor l6 and is mounted on a closed right end of the housing 21.The screw 16 in this conveyor is a choked auger type designed so thatthe choked auger fills the flutes of the screw to act as a gas seal toprevent any vapor from flowing back and into the hopper. When theaggregate in the conveyor reaches the discharge outlet at the right end,the housing 21 is substantially full. Attached to the discharge end ofthe conveyor 16 is a drop chute 26 through which the aggregate is feddownwardly to yet another screw conveyor also of a closed type. Theconveyor is driven by means of a motor 27 through shaft 28 coupled tothe shaft of conveyor 30 disposed to carry the aggregate rightwardly asindicated by the arrow. The housing 32 has its left or drive endparticularly closed or sealed with a cap end 34 adapted to prevent anyescape of any vapor or dust to andout the conveyor. Intermediate theends of the conveyor 30 there is provided a closed heating chamber 40which is sealed to housing 32. In this chamber the aggregate containingthe basic formate of beryllium is heated to a determined degree which iscontemplated to be one hundred fifty to three hundred degreescentigrade. This aggregate is transported by screw 30 so as to be fedthrough this heating chamber 40 with the beryllium basic formate heatedsufficiently to vaporize as described in US. Pat. No. 3,484,278above-identified. The vaporized beryllium basic formate is collected inan upper chamber 42 from whence it is conducted by a duct 44. Theconveyor screw 30 carries the aggregate into the chamber 40 wherein thescrew is continued but the housing 32 is terminated and becomes an opentop trough 41. The trough 41 is preferably constructed of porous metalthrough which heated dry air is passed to vaporize and transport theberyllium basic formate from the aggregate passing along the screwconveyor. The metal trough 41 opens into upper chamber 42 which is anaspirating chamber with duct 43 carrying pressurized gas or air which isdischarged into the vapor conveying duct 44. The aspirating chambercreates a negative pressure above the trough 41 so that the sublimingmaterial as it is volatilized is drawn to duct 44.

After the basic formate of beryllium has been vaporized in heatingchamber 40 the residue containing some organic ash with the balancemainly sand or like inert material is caused to be moved into the closedconveyor 46 and to drop through discharge chute 48 into a return screwconveyor 50 of closed construction and driven by motor 51. The aggregateis delivered for discharge into a drop chute 52 and then into closedaccumulating container 54 where it is retained in a sealed conditionuntil disposal or reclaimation is to be made. Like conveyor 16 thereturn screw conveyor 50 is of the choked auger type which receives theresidue from chute 48 and before discharge through chute 52 the residuefills the conveyor housing. The filled flutes of the choked auger act asa gas seal to prevent any vapor from flowing into accumulating container54.

DEPOSITION CHAMBER OF FIGS. 2 AND 3 Referring now to FIGS. 2 and 3 thereis shown a deposition chamber 55 where vaporized basic formate ofberyllium from the heating chamber 40 is fed through duct 44 into aninner chamber area 60 in which substrates 62 to be plated are placed. Aninner wall 64 is preferably of a porous composition and in the preferredembodiment is shown as a tube. Through this wall dry air and/or any ofseveral gases such a nitrogen, oxygen and the like may be caused to flowunder the influence of a determined amount of pressure. Inner wall 64 issupported and enclosed by an outer housing 66 having end walls sodisposed as to provide a closed gas chamber area 68. Baffles orpartitions 69 are attached to and are carried by outer housing 66 so asto provide conveying passageways for the controlled flow of gas inchamber 68. The baffles may be in the nature of plates radially arrangedin a longitudinal array as in FIG. 3 or, if desired, may be helicallyarranged or may be arranged in other combinations or configurationsproviding for a desired controlled gas flow. These baffles may becontoured on their inner faces to provide a support for tube 64. One ormore inlets 70 are provided in outer housing 66 so that the pressurizeddry air, gas and the like can be fed to the several closed gas chamberareas. An outlet 72 is provided at the end of inner wall 64 which isopposite duct 44 providing the inlet for the vaporized basic formate ofberyllium to the inner chamber.

USE AND OPERATION In the apparatus as shown in FIGS. 1 through 3 andabove-described, an initial aggregate of basic formate of beryllium ismixed with an inert granular material such as sand. The inert materialacts as a carrier for the basic formate and for the granular ash afterto percent of the basic formate of beryllium has been vaporized. Thesystem is sealed at one end by the choked conveyor 16 so that the vaporflow will be caused to go into duct 44 rather than back into the hopper,and so that no dust or vapor can escape to endanger the operator of theequipment. This aggregate is stored in hopper 12 from which it is fedthrough a metering discharge chute 14 to a first conveyor 16. Thisconveyor is sealed as to its housing and the flow of aggregate in theconveyor is sealed by a high level choked auger to prevent any back flowof heated air, vapor and the like from subsequent operations.

From conveyor 16 the aggregate is fed through chute 26 to the conveyor30 which is driven by motor 27 and carries the aggregate into theheating zone of chamber 40. This portion of the conveyor is disposed tospread and agitate the aggregate so that as it is brought into theporous heated trough 41 it is heated as evenly as possible. Thevaporized basic formate of beryllium is drawn into chamber 42 and isthen fed to deposition chamber 55 through flue conductor 44. The residuein conveyor 30 is fed into conveyor section 46 from whence it isdischarged into chute 48 into return conveyor 50. This conveyor is achoked auger preventing any gas flow to subsequent discharge operationsand is of a length and size disposed to cool the residue a determinedamount before it is discharged into chute 52 and accumulating container54.

The vaporized basic formate of beryllium fed to de position chamber 55is brought to and into the inner chamber 62 which is at a temperature oftwo hundred fifty to six hundred degrees centigrade. To prevent thedeposition of BeO on the inner surface of wall of tube 64 the vaporizedbasic formate of beryllium is urged from engagement with the wall bymeans of dry air, nitrogen, oxygen or other gaseous mixtures. This flowthrough the wall provides a gas flow normal to the inner wall of tube 64tending to keep the vaporized basic formate from engagement with thewall. That vaporized beryllium basic formate not deposited on the heatedsubstrates 62 in the inner chamber is fed with the gas flowing throughthe wall to and out exit 72 to a reclaiming process or disposal.

Electronic sensors and controls providing determined rates of flow ofthe aggregate and residue and heating temperatures for both heatingchamber and deposition chamber as well as many other controls have beenomitted from the above drawing and description as these are knowncomponents whose selection and use are determined by the circumstancesof the particular operation and result. Although the conveyors 16 and 50are preferably of the choked auger construction it is also to be notedthat conveyors with metering bulkhead construction may be used toprovide the desired upper seal of the conveyor.

The apparatus above-described has been reduced to practice andextensively and successfully used in vaporizing beryllium basic formate.The basic disclosure of the sublimation of a solid chemical compound asis beryllium basic formate is shown in U.S. Pat, No. 3,484,278 but theapparatus of this invention may be used for other solid sublimablechemical compounds. Examples of said other solid sublimable chemicalcompounds are beryllium acetyl acetonate and acetylacetonato(1,5-cyclooctadiene) iridium. Any oxide of metal or metal alloy can bedeposited by the vapors or organo metallic compounds such as metalalkyates, carboxylates and phenolates. Further compounds are identifiedin a book entitled, Decomposition of Organo Metallic Compounds toRefactory Ceramics, Metals and Metal Alloys". Edited by K. S.Mazdiyasni, published by the University of Dayton Press, (Dayton, Ohio),copyright 1968.

The deposition chamber of FIG. 2 is to be particularly noted. In thischamber pressurized gas or air is passed through the porous wall 64 toprevent unwanted deposition of the vaporized organo-metalloid product onthe inner walls of porous member 64. Conveying means for theto-be-coated product 62 has not been shown as such means is more-or-lessconventional in that the product to be moved and coated will influencethe means selected. The heating chamber 40 and conveyor section 41 arealso constructed in accordance with the characteristics of the infeedingmaterial and the necessary rate of production of the vaporized compound.

Terms such as left, right", up, down, bottom, top", front", back", "in,out and the like are applicable to the embodiment shown and described inconjunction with the drawing. These terms are merely for the purposes ofdescription and do not necessarily apply to the position in which theapparatus for continuously producing and depositing vaporized basicformate of beryllia may be constructed or used.

The conception of the vaporization and deposition apparatus and itsapplication is not limited to the specific embodiment shown butdepartures therefrom may be made within the scope of the accompanyingclaims and without sacrificing its chief advantages and protection issought to be the broadest extent the prior art allows.

What is claimed is:

1. Apparatus providing for a determined continuous production of avaporized solid sublimable organometalloid compound such as berylliumbasic formate, beryllium acetyl acetonate and the like, said apparatusproviding for the delivery of said vaporized material to a depositionchamber, said apparatus including: (a) a hopper providing for the closedstorage of an aggregate which includes a solid sublimableorgano-metalloid compound mixed with a granular inert carrier material;(b) a first conveyor of closed construction disposed to receive acontrolled flow of said aggregate. through a portion of said firstconveyor so as to fill substantially all available passage area so thatthe aggregate at this slowed portion will provide a gas seal to the flowof vapor through said conveyor; (d) a second conveyor of closedconstruction and disposed to receive the discharge of aggregate from thefirst conveyor, said second conveyor disposed to feed said aggregatethrough a closed heating chamber wherein the solid sublimableorgano-metalloid compound is heated sufiiciently to vaporize, (e) acollection chamber in flow communication with the heating chamber anddisposed to receive the vapors from the heating chamber; (f) means toconduct the vapors from the collection chamber to a deposition chamber;(g) a third conveyor of closed construction disposed to receive theresidue from the heating chamber and transport said residue through aportion of said third conveyor; (h) means for slowing the flow ofresidue through the third'conveyor so that substantially all availablepassage area is filled to provide a gas seal to the flow of vaporthrough said conveyor,

and (i) an accumulating closed container disposed to receive the residuefrom the heating chamber and said third conveyor.

2. Apparatus for the production of a vaporized solid sublimableorgano-metalloid compound as in claim 1 in which the means for slowingthe flow of material through the first and third conveyors is by meansof a screw conveyor having a choked auger construction.

3. Apparatus for the production of a vaporized solid sublimableorgano-metalloid compound as in claim 1 in which the means for slowingthe flow of material through the first and third conveyors is by meansof a screw conveyor passing a metering bulkhead construction.

4. Apparatus for the production of a vaporized solid sublimableorgano-metalloid compound as in claim 1 in which the closed heatingchamber includes a trough of porous metal through and around whichheated dry air is forced so as to vaporize the solid sublimableorganometalloid compound and drive the vapor from the aggregate. v

5. Apparatus for the production of solid sublimable organo-metalloidcompound as in claim 4 in which the collection chamber has one side opento the heating chamber, said collection chamber being operated at anegative pressure so that the vaporized solid sublimableorgano-metalloid compound may be moved to and through a duct to an innerchamber area of the deposition chamber.

6. Apparatus for the production of a solid sublimable organo-metalloidcompound as in claim 5 in which the deposition chamber has an inner wallof porous construction surrounded by a closed gas chamber supplied withpressurized gas, air and the like, said gas being permitted toflowthrough the porous inner wall at a rate sufficient to keep thevaporized solid sublimable chemical compound from engagement with theinner surface of the porous inner wall.

7. Apparatus for the production of a vaporized solid sublimableorgano-metalloid compound as in claim 6 in which the closed gas chamberis provided with baffles sposed to direct the flow of pressurized gas ina deterined path

2. Apparatus for the production of a vaporized solid sublimableorgano-metalloid compound as in claim 1 in which the means for slowingthe flow of material through the first and third conveyors is by meansof a screw conveyor having a choked auger construction.
 3. Apparatus forthe production of a vaporized solid sublimable organo-metalloid compoundas in claim 1 in which the means for slowing the flow of materialthrough the first and third conveyors is by means of a screw conveyorpassing a metering bulkhead construction.
 4. Apparatus for theproduction of a vaporized solid sublimable organo-metalloid compound asin claim 1 in which the closed heating chamber includes a trough ofporous metal through and around which heated dry air is forced so as tovaporize the solid sublimable organo-metalloid compound and drive thevapor from the aggregate.
 5. Apparatus for the production of solidsublimable organo-metalloid compound as in claim 4 in which thecollection chamber has one side open to the heating chamber, saidcollection chamber being operated at a negative pressure so that thevaporized solid sublimable organo-metalloid compound may be moved to andthrough a duct to an inner chamber area of the deposition chamber. 6.Apparatus for the production of a solid sublimable organo-metalloidcompound as in claim 5 in which the deposition chamber has an inner wallof porous construction surrounded by a closed gas chamber supplied withpressurized gas, air and the like, said gas being permitted to flowthrough the porous inner wall at a rate sufficient to keep the vaporizedsolid sublimable chemical compound from engagement with the innersurface of the porous inner wall.
 7. Apparatus for the production of avaporized solid sublimable organo-metalloid compound as in claim 6 inwhich the closed gas chamber is provided with baffles disposed to directthe flow of pressurized gas in a determined path